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From "ASF subversion and git services (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (ACCUMULO-112) Investigate partitioning in memory map by locality group
Date Wed, 31 Jul 2013 19:03:51 GMT

    [ https://issues.apache.org/jira/browse/ACCUMULO-112?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13725598#comment-13725598
] 

ASF subversion and git services commented on ACCUMULO-112:
----------------------------------------------------------

Commit 0608e32f8b09f926e40677d1e23ccedd0d6e088d in branch refs/heads/master from [~keith_turner]
[ https://git-wip-us.apache.org/repos/asf?p=accumulo.git;h=0608e32 ]

ACCUMULO-112 added locality group support to in memory map

                
> Investigate partitioning in memory map by locality group
> --------------------------------------------------------
>
>                 Key: ACCUMULO-112
>                 URL: https://issues.apache.org/jira/browse/ACCUMULO-112
>             Project: Accumulo
>          Issue Type: Task
>          Components: tserver
>            Reporter: Keith Turner
>            Assignee: Keith Turner
>              Labels: gsoc2013, mentor
>
> Currently the in memory map is not partitioned by locality group.  This could negatively
impact scan and minor compaction performance.    Would like to run some experiments to understand
the performance implications.  Partitioning by locality group could negatively impact insert
performance, it could go from O(log(R)+log(C))  to O(L * (log(R)+log(C))) in the worst case.
 L is the number of locality groups, R is the number of rows and C is the number of columns.
 The worst case is where each mutation has a change for each locality group. 
> Currently the in memory map is a map of maps.  Like the following.
> {noformat}
>   map<row, map<col, val>>
> {noformat}
> Could conceptually change this to one of the following.  The first is best for scans,
that access some locality groups, and minor compactions.  The second is good for inserts where
the mutation covers all locality groups, because the row is only looked up once.
> {noformat}
>   map<localityGroup, map<row, map<col, val>>>
> {noformat}
> {noformat}
>   map<row, map<localityGroup, map<col, val>>>
> {noformat}
> The Accumulo native map is implemented using C++,STL, JNI, and with thread locking in
java.

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